The invention relates to a jig system adapted for connection to an intramedullary nail, wherein the intramedullary nail is implanted in a fractured bone, such as a tibia, the implantation being such as to have the nail extend distally and proximally with respect to the fracture, in reinforcement of fractured parts of the bone that have been re-aligned or merely are to be held in alignment for the course of healing repair.
Intramedullary nails of the character indicated are either solid or hollow, but they are customarily prepared with two spaced parallel holes that extend diametrically across the nail near the distal end of the nail and with two spaced holes of similar nature, but not necessarily parallel, near the proximal end of the nail. These holes are formed to accept bone screws, and when the nail has been installed, its bone-screw holes are said to be "blind" in terms of the bone-drilling alignment that must be achieved. The problem has always been one of assuring correct alignment for drilling to accept a bone screw driven through bone for anchoring passage through the intramedullary nail. The traditional technique for assuring blind drill alignment with the bone-screw holes of an intramedullary nail involves use of x-rays, which of course pose well-known dangers from cumulative exposure; and to assure adequate safety for operating personnel, the use of x-rays is, to say the least, cumbersome, thus contributing to the expense of a good intramedullary-nail installation.
The proximal end of the nail is formed for anti-rotational keyed and detachably fixed connection to jig structure that is intended to aid in orientation of drill guides in the hope of achieving a correct alignment with each drill hole, the customary technique of ascertaining alignment being by use of x-rays.
One of the problems of locating a bone-screw hole in an installed intramedullary nail is the practical fact that the nail may have undergone a slight bend in the course of implantation, so that such holes at the distal end of the nail no longer have precisely the same location with respect to the proximal end, as was the case prior to nail implantation. Thus, any jig structure connected to the proximal end has had to rely on x-rays for assurance of alignment.
In an effort to avoid x-ray dependance in solving the problem of locating blind bone-screw holes in an installed intramedullary nail, U.S. Pat. No. 5,281,224 and pending U.S. application Ser. No. 08/121,762 have proposed magnetic detection, in the scanning displacement of a detection system across the distal region of an installed nail, to locate the central axis of the nail; but in the present state of development, such techniques have been clinically awkward, achieving less than the accuracy that is required.